What techniques are used to tackle inferior calyceal stones in Retrograde Intrarenal Surgery (RIRS)?

Techniques for Inferior Calyceal Stones in RIRS

For inferior calyceal stones during RIRS, the optimal approach combines stone relocation to a favorable position (renal pelvis or upper calyx) before fragmentation, followed by complete laser lithotripsy using Ho:YAG or Thulium fiber laser, with selective use of large ureteral access sheaths (14-16F) for stones >20mm and adjunctive techniques like autologous blood clot occlusion to prevent fragment reaccumulation. 1, 2, 3

Core Technical Approach

Stone Relocation Strategy

• Relocate inferior calyceal stones to the renal pelvis or superior calyx BEFORE initiating fragmentation to protect the flexible ureteroscope from damage and improve stone-free rates 4, 5
• Use a nitinol basket for stone relocation, which is required in approximately 60% of cases 3
• This maneuver is essential because in situ treatment of inferior calyx stones significantly increases risk of scope damage 4

Laser Lithotripsy Technique

• Ho:YAG laser remains the gold standard for stone fragmentation during RIRS 1
• Thulium fiber laser offers comparable efficacy as an alternative 1
• High-power settings reduce lasering time but have no proven clinical advantage over standard settings 1
• Fragment stones to <3mm size to facilitate spontaneous passage 3
• Complete stone removal is the primary goal; "dust and go" technique should be limited to large renal stones 1

Advanced Technical Modifications

Large Ureteral Access Sheath Technique

For stones >20mm, consider the combined semirigid and flexible ureteroscopy approach:

• Use a large-lumen ureteral access sheath (14/16F, 35cm) after preoperative ureteral stenting 6
• This technique provides superior irrigation and outflow, enhancing both vision and stone clearance 6
• Allows multiple ureteral passages without injury risk 6
• Achieves stone-free rates of 81.8% at 3 months for stones 20-60mm 6

Autologous Blood Clot Occlusion Technique

When complete fragment removal is not feasible:

• Fill the inferior calyx with 5-10cc of venous autologous blood with patient in reverse Trendelenburg position 3
• Allow blood to clot in situ to prevent fragment reaccumulation in the inferior calyx 3
• Confirm occlusion with pyelogram before placing DJ stent 3
• This technique achieves 94% stone-free rate at 3 months and 97% at 6 months 3
• Minimizes ureteral trauma from multiple instrument passages needed for active fragment removal 3

Alternative Fragment Retrieval: Glue-Clot Technique

• For small calyceal stone fragments that are difficult to remove, the glue-clot technique provides a simple and efficient retrieval method 7
• This addresses the challenge that direct fragment removal requires many ureteroscope passages and is time-consuming 7

Clinical Decision Factors

Stone-Specific Considerations

• Stone density (Hounsfield units) and location significantly affect outcomes 5
• Lower pole stones negatively affect RIRS success rates compared to other locations 5
• Stones with HU <677 may have reduced stone-free rates 5
• For lower pole stones 10-20mm, RIRS achieves median success rates of 81% versus 87% for PCNL 2

Stenting Strategy

• Preoperative ureteral stenting is recommended but not mandatory; it may improve treatment outcomes for renal stones 1, 6
• Routine post-RIRS stenting is unnecessary after uncomplicated procedures and may increase morbidity 1
• Stenting is mandatory in cases with trauma, residual fragments, bleeding, perforation, UTI, or pregnancy 1
• Alpha-blockers improve stent tolerability and facilitate stone fragment passage 1, 2

Critical Safety Considerations

Infection Management

• If purulent urine is encountered, immediately abort the procedure, establish drainage (stent or nephrostomy), and continue antibiotics 1
• Antimicrobial prophylaxis must be administered within 60 minutes of procedure based on prior culture results 1

Procedural Safeguards

• Always use a safety guidewire during RIRS to facilitate rapid re-access if the primary wire is lost and provide access in case of perforation or injury 1
• Preoperative CT or ultrasound helps identify interposed organs 1

Common Pitfalls to Avoid

• Do not attempt in situ fragmentation of inferior calyceal stones without first attempting relocation - this dramatically increases scope damage risk 4
• Avoid excessive instrument passages for fragment removal when autologous blood clot occlusion can achieve similar stone-free rates with less trauma 3
• Do not offer RIRS as first-line for stones >20mm without considering PCNL, which has superior stone-free rates (87% vs 81%) 2
• Recognize that lower pole location is an independent negative predictor of RIRS success 5